Information transmission system

ABSTRACT

An information transmission network in which a plurality of information processing stations are connected in parallel to a bus line is disclosed. Each station has a communication control means and an information processor. Each control means is capable of establishing command over the bus line to the exclusion of all other stations. While command is established, the commanding station can communicate with all other stations. After one sequence of communication, command is transferred. If the station presently in command fails, the failure to transfer command in a predetermined time will be noted and another station with highest priority will assume command. If the station to which command is transferred is not operating properly, the station presently in command will detect a failure of the former station to respond to transfer of command and will thereupon transfer command to another station.

BACKGROUND OF THE INVENTION

This invention relates to an information transmission system wherein aplurality of information processing apparatuses distributed over a widearea are connected in parallel with each other via a commonly providedinformation transmitting bus line, and information is arbitrarilytransmitted between these information processing apparatuses.

In the case where a plurality of information processing apparatuses aredistributed over a comparatively wide area so that each of theapparatuses is separated from others by comparatively long distances,interconnection of all the information processing apparatuses throughseparate transmission lines is not economical because such anarrangement not only requires a greater amount of transmission lines butalso requires the provision of a plurality of information transmittingdevices in each apparatus. To eliminate the latter disadvantage of theabove described arrangement, there has been proposed an informationtransmitting system of the type shown in FIG. 1, wherein a plurality ofinformation processing apparatuses, 1 through N, are connected inparallel with a common information transmitting bus line CL. Under thecontrol of a bus line control device LC, information transmissionbetween these apparatuses is arbitrarily carried out over the bus lineCL.

However, such an information transmitting system requires a bus linecontrol device, LC, capable of supervising and controlling the bus lineagainst duplicate use of the bus line, and any trouble in the bus linecontrol device, LC, tends to cause a total failure of the informationtransmitting system. For this reason, the bus line control device LC ismade of high precision circuits operable in a multiplex manner, thusrequiring a high cost of manufacture.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a novel informationtransmitting system wherein a common information transmitting bus lineis used without requiring a costly bus line control device, informationtransmission can be achieved between any of the plurality of informationprocessing apparatuses, and any possibility of causing total failure ofthe system by a single error can be eliminated.

For the achievement of the above-mentioned object, the informationtransmission system according to this invention is characterized in thateach of the information processing apparatuses is provided with meanscapable of establishing a command over the information transmitting busline. Under such command information is transmitted between the sameinformation processing apparatus, now establishing command, and anotherinformation processing apparatus. After the termination of theinformation transmission, the command of the information transmittingbus line is sequentially transferred from the apparatus havingestablished command over the information transmitting bus line to otherinformation processing apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the construction of a conventionalinformation transmission system;

FIG. 2 is a block diagram showing the construction of the informationtransmission system according to the present invention;

FIG. 3a is a time chart showing signals present on the bus line whenstation 1 in FIG. 2 has established command;

FIG. 3b is a time chart showing the signals present on the bus line whenstation 2 in FIG. 2 has established command;

FIG. 3c is a time chart showing signals present on the bus line whenstation 3 in FIG. 2 has established command; and

FIG. 4 is a block diagram showing a concrete example of the informationprocessing apparatus according to this invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2 is a block diagram showing the basic construction of theinvention. In the figure, 1 through N designate information processingapparatuses comprising respectively communication controls TR1 throughTRN, each having a bi-directional communication function, andinformation processing portions A₁ through A_(N). The apparatuses areconnected in parallel through the communication controls TR₁ throughTR_(N) with a commonly provided information transmitting bus line CL.The communication control TR or each information processing apparatusfunctions not only to transmit information between the informationprocessing portion A and the bus line CL, but also to establish commandover the bus line. When the communication control means TR establishescommand over the bus line CL, it delivers, by the request of informationprocessing portion A, an information transmitting instruction towardanother information processing apparatus, and actively operates totransmit and receive information for the information processing portionA. When the communication control means TR does not establish commandover the bus line, it obeys the instruction from another informationprocessing apparatus which establishes command over the bus line andpassively operates in transmitting and receiving information for theinformation processing portion A. The information processing apparatusesare assigned with their own addresses 1 through N, respectively, andwhen a communication control means TR transmits information over the busline CL, an address designating the destined information processingapparatus is added to the information. When the communication control TRreceives information from the bus line CL, it selectively receivesinformation having an address assigned to it.

One example of the information transmitting procedure in the systemaccording to this invention is indicated in FIG. 3.

It is first assumed that the communication control means TR₁ of the No.1 information processing apparatus 1 establishes command over the busline CL. This is realized by a command establishing signal ELS₁delivered from the communication control means TR₁ over the bus line asshown in FIG. 3a. The communication control means TR of the otherinformation processing apparatuses reset their own command establishingdevices thereby to prevent duplicated establishment of command over thebus line. In the case where the information processing portion A₁ of theinformation processing apparatus 1 has data DT₂ to be transmitted to theinformation processing apparatus 2, the communication control means TR₁delivers a transmission request signal SEQ₂ including the address 2 ofthe information processing apparatus 2. Upon receiving the transmissionrequest signal SEQ₂, the communication control means TR₂ of theinformation processing apparatus 2 detects that the signal is directedto its own apparatus 2, and when the apparatus 2 is in a receivablestate, the communication control means TR₂ delivers a reception readysignal ACK₂ over the bus line. When the communication control means TR₁receives the reception ready signal ACK₂ from TR₂, it reads out the dataDT₂ from the information processing portion A₁ and transmits the samethrough the bus line to the information processing apparatus 2. Thecommunication control TR₂ of the apparatus 2 receives the data DT₂ andchecks for errors to confirm the correctness of the received data. Whenthe confirmed data is written into the information processing portion A₂of the apparatus 2, the communication control means TR₂ delivers areception completion signal RAK₂ over the bus line CL. When thecommunication control TR₁ receives the reception completion signal RAK₂,a series of data transmission procedures terminates. The communicationcontrol means TR₁ thus terminates the data transmission, then transfersthe command of the bus line in accordance with a predeterminedsequential order or utterly arbitrarily to, for instance, theinformation processing apparatus 2 by sending a command transferringsignal SEL₂. Simultaneously, the command establishing device in thecommunication control means TR₁ is reset.

The communication control means TR₂ of the apparatus 2, upon receptionof the command transferring signal SEL₂, sets the command establishingdevice and then delivers a command establishing signal ELS₂ as shown inFIG. 3b over the bus line CL. The command of the bus line by thecommunication control means TR₂ is thus established. However, if thereis no demand for data transmission in the information processingapparatus 2, the communication control means TR₂ immediately delivers acommand transfer signal SEL₃ to the communication control means TR₃ ofthe apparatus 3.

Upon reception of the command transfer signal SEL₃, the communicationcontrol means TR₃ sets the command establishing device and delivers acommand establishing signal ELS₃ as shown in FIG. 3c over the bus lineCL. When the apparatus 3 has a demand to read out the data in theinformation processing apparatus N, the communication control TR₃delivers a reception request signal REQ_(N) directed to thecommunication control TR_(N) of the apparatus N over the bus line. Whenthe apparatus N is in a transmissible state, the communication controlmeans TR_(N) which has received the reception request signal REQ_(N),immediately reads out the data DT_(N) stored in the informationprocessing portion A_(N) and transmits the same to the communicationcontrol means TR₃. The communication control means TR₃ receives the dataDT_(N), checks for error, and if any error is found, delivers areception reclaiming signal ARQ_(N) toward the communication controlmeans TR_(N). The communication control means TR_(N) thus retransmitsthe data DT_(N), and when the data DT_(N) is correctly received by thecommunication control means TR₃, the data is transferred into theinformation processing portion A₃, and the series of data transmittingoperations terminates. The communication control means TR₃ resets itsown command establishing device and delivers a command transferringsignal SEL₄ toward the subsequent information processing apparatus 4.

From the above description, it will be apparent that informationtransmission can be carried out between any arbitrary pair ofinformation processing apparatuses by repeating the above describedprocedures.

In FIG. 4, an example of the communication control means included ineach information processing apparatus is indicated in block diagramform, where each block represents a known device. In the drawing, CLdesignates the commonly provided information transmitting bus line, Athe information processing portion, and TR the communication controlmeans connected with the information processing portion A through datalines D₅ and D₆ and control lines G₁ through G₄. The communicationcontrol TR has a receiver RED and a transmitter SED both connecteddirectly to the common bus line CL. When it is required, the receiverRED and the transmitter SED can modulate and demodulate the relatedsignals. The output side of the receiver RED is connected with areceiving register RD₁ made of a shift register for the series-parallelconversion of the output signal. More specifically, when the registerRD₁ stores one word or one block of information having a predeterminednumber of bits, it delivers a buffer-full signal BF_(R) toward areception control device C₁ thereby to report the reception ofinformation. Upon reception of the buffer-full signal BF_(R), thereception control device C₁ reads out the data stored in the registerRD₁ in parallel, and carries out interpretation and error checkoperations on the data. The reception control device C₁ furthergenerates various control signals depending on the results of suchoperations, and sends these signals to a command establishing device M,timers T₁ and T₂, a transmission control device C₂, and a received databuffer register RD₂ .

The transmission control device C₂ delivers various control data inaccordance with the control signals from the reception control deviceC₁, command establishing device M, timers T₁ and T₂, and adds an addressof destination to the data read out of a transmission data bufferregister, the resultant data being delivered in parallel to atransmitting register SD₁ which is made of a shift register toeffectuate parallel-series conversion on the resultant data. When thedata is stored in the transmitting register SD₁, the same registerdelivers a buffer-full signal BF_(S) causing the transmitter SED to readout the data bit by bit in series from the register SD₁ and to transmitthe data over the bus line CL.

Furthermore, AD₁ designates an own address setting device, and AD₂designates a subsequent address setting device which sets the address ofan information processing apparatus to which the command for controllingthe bus line is to be transferred. The times T₁ and T₂ are provided forsupervising the bus line for the purpose of preventing interruption ofdata transmission due to the fault of the communication controlpresently having command or the communication control to which thecommand is to be transferred.

The operation of the communication control is as follows.

When a command transfer signal SEL is delivered to the bus line CL fromthe communication control means of the apparatus presently havingcommand over the bus line, receivers RED in the communication controlmeans TR of all the information processing apparatuses receive thecommand transfer signal SEL and store the same in their receivingregisters RD₁. When the receiving register RD₁ stores a predeterminednumber of bits of the signal, a buffer-full signal BF_(R) is deliveredto the reception control device C₁. Upon reception of the buffer-fullsignal, the reception control device C₁ starts to operate to read outthe data stored in the register RD₁, to interpret the control signalsincluded in the data, and to compare the address attached to the datawith its own address. As a result, the reception control device C₁ inthe communication control means whose address coincides with the addressattached to the data SEL delivers a command setting signal S₁ to theinput of the command establishing device M. The command establishingdevice M is thereby set, and the communication control means TR of theinformation processing apparatus establishes command over the bus line.

Setting of the command establishing device M causes it to deliver asignal S₂ toward the transmission control device C₂ thereby to instructthe transmission of a command establishing signal ELS, having its ownaddress attached thereto, which is given by the own address settingdevice AD₁. The transmission control device C₂ effectuates the addressattaching operation, and the resultant signal is sent through the dataline D₃ to the transmission register SD₁ under the condition of theregister SD₁ being still vacant. When the signal is stored in thetransmission register SD₁ and a buffer-full signal BF_(S) is deliveredto the transmitter SED, the latter starts to operate therebytransmitting the signal stored in the register SD₁ bit by bit in seriesover the information transmitting bus line CL. By the transmission ofthe signal ELS attached with the address of the information processingapparatus, the fact that the communication control means TR hasestablished command over the bus line CL is reported to thecommunication control means TR of all the other information processingapparatuses.

When the command establishing signal ELS from the communication controlTR of the information processing apparatus now establishing command overthe bus line is received in all the remaining information processingapparatuses through the receiver RED and the receiving register RD₁, thereception control device C₁ delivers a signal S₃ to reset the commandestablishing device M because the address attached to the signal ELSdoes not coincide with its own address. At this time, in thecommunication control TR means of the information processing apparatusnow having established command, the reception control device C₁ does notdeliver the signal S₃ and the command establishing device M is held inthe set state. Thus, the communication control TR from which the commandestablishing signal ELS is delivered acquires the command of thetransmission bus line CL and can operate actively to control the busline.

After the transmission of the command establishing signal ELS from thecommunication control means TR, the transmission register SD₁, now in avacant state, delivers a buffer empty signal BE_(S). Upon reception ofthe buffer empty signal BE_(S), the transmission control device C₂surveys the existence or nonexistence of data in a transmitting databuffer register SD₂ depending on the state of a data existenceindicating signal S₁₀. In the transmitting data buffer register SD₂,data from the information processing portion A, when such a demandexists in the portion A, has been sent through a data line D₆ togetherwith the address of the destined information processing apparatus andstored therein. When the data buffer register SD₂ stores such data, itdelivers the signal S₁₀ in the "1" state, and when it does not storesuch data it delivers the signal S₁₀ in the "0" state. Now it is assumedthat data from the information processing portion A is stored in thebuffer register SD₂, and the signal S₁₀ is in the "1" state. Thetransmission control device C₂ knows of the existence of such data fromthe "1" state of the signal S₁₀ and instantaneously reads out theaddress of the destined information processing apparatus stored in thebuffer register SD₂ together with the data to be transmitted. Thecontrol device C₂ further attaches this address to a transmissionrequest signal SEQ and sends out the resultant signal to thetransmission register SD₁ through the data line D₃. The transmitter SEDtransmits the signal in the transmission register SD₁ over thetransmission bus line CL.

The reception control device C₁ in the communication control means TR inthe other information processing apparatuses which have received thetransmission request signal SEQ interpret the signal SEQ andsimultaneously therewith compare the address attached to the signal withtheir own address. When the two addresses coincide, the receptioncontrol device C₁ operates as indicated by the signal SEQ. That is, thedevice C₁ surveys the existence or nonexistence of data in the receiveddata buffer register RD₂ from the condition of the data existenceindicating signal S₁₁. The received data buffer register RD₂ temporarilystores data received and transfers the data under the control of thereception control device C₁ to the information processing portion Athrough the data line D₅. When data is stored in the buffer registerRD₂, the latter delivers the signal S₁₁ in the "1" state, and when nodata is stored, it delivers the signal S₁₁ in the "0" state.

When the signal S₁₁ is in "0" state indicating a vacancy of the bufferregister RD₂, the reception control device C₁ sends out a responseinstruction signal S₄ in "1" state to the transmission control deviceC₂, and when the signal S₁₁ is in "1" state indicating the bufferregister RD₂ is not vacant, the device C₁ sends out the responseinstruction signal S₄ in "0" state to the transmission control deviceC₂. The transmission control device C₂ generates a reception readyresponse signal ACK when the signal S₄ is "1", and a reception not readyresponse signal NAK when the signal S₄ is "0", and sends the signal ACKor NAK to the transmission register SD₁. The transmitter SED sends outthe response signal ACK or NAK over the transmission bus line CL to thesource of the transmission request signal SEQ, that is, the apparatusnow establishing command over the bus line CL.

In the information processing apparatus now establishing command, whenthe communication control means TR interprets that the response signalsent from the communication control means in the destined aparatus isthe reception ready signal ACK, the reception control device C₁ deliversa data transmission instruction signal S₅ to the transmission controldevice C₂ in the same TR. The transmission control device C₂ thus readsout the data attached with the address of the destination apparatusstored in the buffer register SD₂, and sends the data to thetransmission register SD₁. The transmitter SED in turn sends out thedata attached with the address of the destination over the bus line CL.

In the communication control TR of the destination apparatus, the datathus transmitted over the bus line CL is received through the receiverRED and reception register RD₁. When the reception control device C₁judges that the address attached to the data now received coincides withits own address, the data in the reception register RD₁ is transferredthrough the data line D₂ to the reception buffer register RD₂. When adata transmission termination signal ETX from the transmitting apparatusis received in the TR of the destination apparatus, the receptioncontrol device C₁ carries out error check on the data stored in thebuffer register RD₂, and depending on whether error is found or notfound, the control device C₁ delivers a reception response instructionsignal S₆ in "0" or "1" state, respectively, toward the transmissioncontrol device C₂. The device C₂ thus sends out through the transmitterSED a reception completion signal RAK when the instruction signal S₆ isin "1" state, and a reception incorrect signal RNK when the instructionsignal S₆ is in "0" state, over the transmission bus line CL.

When the communication control TR in the information processingapparatus now establishing command receives the reception completionsignal RAK or the reception incorrect signal RNK sent from the TR of thedestination apparatus after the former control TR has transmitted thedata, it operates as follows. The reception control device C₁ in thecommunication control TR interprets the content of the signal receivedthrough the receiver RED and stored in the reception register RD₁, andif it finds out that the signal is the reception completion signal RAK,a transmission completion instruction signals S₇ is sent from the deviceC₁ to the transmission control device C₂. The transmission controldevice C₂ thus detects that the series of data transmission hasterminated, and sends out a reset signal S₁₂ to the tranmission bufferregister SD₂ to reset the same, and also another reset signal S₈ to thecommand establishing device M to reset the same device for releasing theestablishment of the command. Simultaneous therewith, the transmissioncontrol device C₂ delivers a command establishing signal ELS attachedwith an address beforehand set in the subsequent address setting deviceAD₂ to be sent out through the transmitter SED over the transmission busline CL.

On the contrary, when the reception control device C₁ judges that thecontent of the response signal is the reception incorrect signal RNK,the reception control device C₁ delivers the data transmissioninstruction signal S₅ toward the transmission control device C₂. Thetransmission control device C₂ thus reads out the data stored in thetransmission buffer register SD₂ and carries out the retransmission ofthe same data. In the case where the reception completion signal RAKcannot be obtained from the destination apparatus even after repetitionof the retransmission procedure for a predetermined number of times, thetransmission control device C₂ sends a signal C₁ to the informationprocessing portion A thereby to inform the portion A of the fact thatthe transmission of the data was unsuccessful, and also sends a resetsignal S₈ to the command establishing register M to release theestablishment of the command. Simultaneous therewith, the transmissioncontrol device C₂ generates a command establishing signal ELS andattaches thereto an address beforehand set in the subsequent addresssetting device AD₂ and sends out the resultant signal through thetransmitter SED to the transmission bus line CL.

The communication control means TR operates as described during theperiod from the establishment of the command to the release of the same.In the case where command is established in the communication controlmeans TR but the information processing portion A has no demand totransmit data, and in the case where after transmission of thetransmission request signal SEQ a reception not ready signal NAK isreceived from the destination apparatus, the reception control device C₁in the communication control TR immediately delivers a command releasingsignal S₃ to the command establishing register M. The command is thusreleased and transferred to the subsequent information processingapparatus as described hereinbefore. Furthermore, the communicationcontrol may be so constructed that when it receives a data receptionrequest signal REQ from the communication control TR of otherinformation processing apparatus establishing command, it reads out thedata stored in the transmission data buffer register SD₂ and sends thedata toward the communication control TR of the information processingapparatus now establishing command. When so constructed, thecommunication control TR of an information processing apparatusestablishing command can operate in both of requesting data transmissionto any other apparatus and requesting data reception from any otherapparatus.

The communication control TR of an information processing apparatus thusaquires the command by the command transferring action of theinformation processing apparatus establishing command, and once thefirst information processing apparatus aquires the command, it canoperate actively in requesting other apparatus to transmit and receivedata. When there is no demand to transmit or receive data in its ownapparatus or when a series of data transmission operations based on thedemand has terminated, the communication control means TR operatesimmediately in transferring the command to another informationprocessing apparatus in a predetermined sequence. Thus it is apparentthat every individual information processing apparatus indicated in FIG.2 can transmit its data under the above described operation of thecommunication control of the apparatus with the command over thetransmission bus line transferred in a predetermined sequence.

All the above described operations of the information processingapparatuses are based on the assumption that the communication controlof each information processing apparatus has no fault and therefore canoperate normally. However, if a fault occurs in any of the communicationcontrol means of these apparatuses, there is a possibility of thecommand transferring action becoming impossible, as will be mentionedbelow.

Firstly, when a fault occurs in the communication control of aninformation processing apparatus presently in command, the commandtransferring signal SEL for transferring the command to the subsequentapparatus cannot be issued from the faulty communication control whichmakes it impossible to transfer the command. Secondly, when a faultoccurs in the communication control means in the information processingapparatus to which the command is to be transferred, the commandestablishing signal ELS will not be received and acted upon thus alsomaking it impossible to transfer the command. When the transfer ofcommand is made impossible as described above, the informationprocessing apparatus having command disappears and the transmission ofdata between the information processing apparatuses is interrupted, thuscausing the total failure of the system.

In order to prevent the total failure of the system caused by the faultsin the communication controls of the information processing apparatuses,timers T₁ and T₂ constituting a watch mechanism are provided as shown inFIG. 4 in the communication control means.

The timer T₁ in the communication control TR is set to a time length Taslightly longer than that of one word or one block of words used in eachof the information processing apparatuses. The time length Ta is varieddepending on the priority for transferring the command to theinformation processing apparatus. More specifically, the time length Tais made shorter when the command transferring priority of the giveninformation processing apparatus is high. The timer T₁ is started by S₁or S₃. After the termination of the time length Ta of the timer T₁, asignal ST₁ is delivered from the timer T₁. However, the timer T₁ may berestarted before the termination of the time period Ta if a reset orrestart signal is applied thereto, and in this case the time countingoperation of the timer T₁ is restarted from zero. The S₁ delivered fromthe reception control device C₁ when it receives command transferringsignal SEL destined for itself and the signal S₃ also delivered from thereception control device C₁ when the latter receives a commandestablishing signal ELS from any other apparatus are used for the timerreset signal. The output signal ST₁ from the timer T₁ is applied to thecommand establishing device M as a set signal.

On the other hand, the timer T₂ is set to have a time length Tb slightlylonger than that required for receiving the command establishing signalELS from another information processing apparatus after the commandtransferring signal SEL has been sent. The timer T₂ operates in such amanner that it starts its time counting operation from the instant whenthe transmission control device C₂ delivers a timer set signal S₉simultaneous with the delivery of the command transferring signal SEL.It delivers a time output signal ST₂ at the termination of the presettime length Tb. However, if the timer T₂ receives a reset signal fromthe reception control device C₁ during its time counting operation, thetimer T₂ is reset thereby to stop the time counting operation. Theoutput signal ST₂ from the timer T₂ is applied to the transmissioncontrol device C₂ as an instruction signal for the jumped transfer ofthe command. When the transmission control device C₂ receives the signalST₂ from the timer T₂, it operates to transmit a command transferringsignal SEL attached with an address beforehand set in the subsequentaddress setting device AD₂ plus one.

When all the communication controls of the information processingapparatuses are operating in normal manner, the reception control deviceC₁ in the communication control of each of the information processingapparatuses receives the command transferring signal SEL or the commandestablishing signal ELS within a shorter period than the time period Taset in the timer T₁, a reset signal S₃ or a set signal S₁ for thecommand establishing device M is delivered in correspondence therewith,and either one of the signals is applied to the reset input of the timerT₁, whereby the timer T₁ has no possibility of generating the outputsignal ST₁, and the command establishing device M is never set by thetimer T₁.

However, if a fault occurs in the communication control means TR of theinformation processing apparatus now establishing command, and nocommand transferring signal SEL is delivered from the communicationcontrol TR toward the information processing apparatus to which thecommand is to be transferred subsequently within the due time, nocommand transferring signal is emitted from any of the informationprocessing apparatuses. In this situation, timers T₁ in thecommunication controls TR of the information processing apparatusessuccessively arrive at the ends of their time periods Ta set therein.However, the timer within the communication control TR of an informationprocessing apparatus having the highest priority delivers firstly theoutput signal ST₁ and the command establishing device M in thecommunication control TR is thereby set to establish command by the sameinformation processing apparatus. Thus the command establishing signalELS is immediately delivered from the communication control means of thesame information processing apparatus, and since the communicationcontrol means of other information processing apparatuses receive thecommand establishing signal ELS before the termination of the timeperiods Ta set in their timers T₁, the timer T.sub. 1 in thesecommunication control means are all reset. Thus it is apparent that whenthe transfer of command becomes impossible by a fault in thecommunication control TR in the information apparatus now establishingcommand, the command is automatically transferred to one of the normallyoperating information processing apparatuses having the highestpriority, the subsequent operations being carried out as describedhereinbefore.

When a fault occurs in the communication control TR in an informationprocessing apparatus to which command is subsequently to be transferred,command is transferred jumping over the faulty communication controlmeans TR to another information processing apparatus to which thecommand is to be transferred. That is, in the communication controlmeans TR which delivers the command transferring signal SEL to theinformation processing apparatus set in the subsequent address settingdevice AD₂, the transmission control device C₂ delivers simultaneoustherewith a set signal S₉ to the timer T₂ thereby to set the timer intoits time counting operation. If no signal for establishing command ELSis received in the communication control means TR from the informationprocessing apparatus set in the subsequent address setting device AD₂because of a fault in the communication control means TR of the latterapparatus within the time period Tb, the timer T₂ will deliver an outputsignal ST₂ to the transmission control device C₂. Upon reception of thesignal ST₂, the transmission control device C₂ adds one to the addressset in the subsequent address setting device AD₂, and acts to transmitagain another command transferring signal SEL attached with the addressthus added with one over the transmission bus line CL, thereby totransfer command in jumping over the information processing apparatusset in the subsequent address setting device AD₂ to the secondsubsequent information processing apparatus. Thus, it is apparent thateven in the case of a fault in the communication control means TR towhich the command is to be transferred, command is transferred by theoperation of the timer T₂ in jumping manner to the second subsequentinformation processing apparatus without causing any interruption of thedata transmission.

The data transferring operation between the communication control meansTR and the information processing portion A, both included in the sameinformation processing apparatus, will now be described somewhat indetail.

In the data transmitting operation, the information processing portion Adetects a signal G₂ indicating the vacancy of the buffer register SD₂,and when the signal G₂ is in the state showing the vacancy, the portionA sets the data into the transmission buffer register SD₂. The registerSD₂ sends the signal S₁₀ in the state "1" showing the possession of datato the transmission control device C₂ when the data setting operation ofthe portion A terminates. The transmission control device C₂ sends areset signal S₁₂ to the register SD₂ when the data transmission of thedata set in the register SD₂ completes thereby to reset the bufferregister SD₂ to prepare for the subsequent data.

In the data reception operation, when received data is taken into thereception buffer register RD₂, the register RD₂ sends out a receptioncompletion signal G₃ to the information processing portion A. Uponreception of the signal G₃, the information processing portion A readsout the data through the data line D₅, and when the reading operationcompletes, the information processing portion A sends a reset signal G₄to the buffer register RD₂ for preparing the register to store thesubsequent data.

As will be apparent from the above description, according to thisinvention, a plurality of information processing apparatuses areconnected in parallel with a commonly provided transmission bus line,and data are transmitted and received between these informationprocessing apparatuses in a manner such that each of the informationprocessing apparatuses sequentially establishes the command of thetransmission bus line and carries out transmission of data with otherinformation processing apparatuses. Thus, the requirement of a commonlyprovided bus line control device in the conventional arrangement isobviated and the cost for the entire information transmission system canbe economized. Furthermore, when any fault occurs in the informationprocessing apparatus, the command for the bus line is established in amanner jumping over the faulty information processing apparatus, anddata can be transmitted and received between the remaining informationprocessing apparatuses.

Although C₁ and C₂ are shown as single blocks, respectively, it will beappreciated by anyone of ordinary skill in the art that the latter theblocks may consist of several individual commonly used elements forcarrying out the conventional functions ascribed to C₁ and C₂, e.g.decoding a given signal and outputing a certain S pulse in responsethereto, responding to a given S pulse by generating a preset pulsecode, etc.

What is claimed is:
 1. In an information transmission network of thetype comprising a plurality of information processing stations, eachhaving a communications control means and an information processor,linked together by their parallel connection to an information bus line,a method of establishing orderly command over the utilization of saidbus line without a special line controlling station, said methodcomprising,a. establishing at a given station i command over the use ofthe bus line, b. transmitting to said bus line from said given station ia command established signal ELS indicating that command is establishedand that said given station i has command, c. receiving at all otherstations said command established signal ELS, d. communicating databetween said given station i and any other station via said bus line, e.after said communication or where no communication is required bystation i, relinquishing command and sending a transfer command signalSEL having a selected address m attached thereto to said bus line, f.receiving at all stations said transfer command signal SEL, and at thestation having address m establishng command over the bus line, and g.repeating steps (b) thru (e) with station m being the command station,whereby command is continuously transferred from one station to the nestto give all stations command of the bus line consecutively.
 2. Themethod of claim 1 further comprising a method of detecting failure atthe station presently commanding the bus line, said method of detectngcomprising,a. monitoring at each station the SEL and ELS signals on thebus line, b. noting the absence of either of said latter signals for afirst predetermined period of time longer than that required for anystation to take command, communicate with another station and relinquishcommand; said predetermined period being different at each station, c.establishing command and sending to the bus line an ELS signal at thestation where the said first predetermined period has been exceeded. 3.The method of claim 2 further comprising a method of detecting failureat the station to which command is to be transferred, said methodcomprising the steps of,a. starting a timer at the station presently incommand when said station presently in command send a transfer commandsignal SEL with the address of the transferee station to the bus line,b. stopping said timer upon receipt of a signal ELS via the bus line, c.after a second predetermined time, longer than that required to send anSEL signal and receive an ELS signal, during which no ELS signal hasbeen received at the station transferring command, retransmitting atransfer command SEL with the address of a different station to the busline.
 4. The method of claim 1 further comprising a method of detectingfailure at the station to which command is to be transferred, saidmethod comprising the steps of,a. starting a timer at the stationpresently in command when said station presently in command sends atransfer command signal SEL with the address of the transferee stationto the bus line, b. stopping said timer upon receipt of a signal ELS viathe bus line, c. after a second predetermined time, longer than thatrequired to send an SEL signal and receive an ELS signal, during whichno ELS signal has been received at the station transferring command,retransmitting a transfer command SEL with the address of a differentstation to the bus line.